Snap drum switch



\ oNirEo STATES CURTISS F. SMITH, 0F DETROIT, MICHIGAN.

SN AP DRUM SWITCH.

Specification of Letters Patent.

Patented May 23,1922.

Application led February 21, 1921. Serial No. 446,811.

To all who/m. t may concern Be it linown that I, Cinrriss F. SMITH, a citizen ot the United CStates ot America, residing at Detroit, inthe county ot lllayne and vState ot lllichigan, have invented certain new andL useful Improvements in Snap Drum Switches, ot which the 'tollowing is a specification, reference being had therein to the accompanying drawings.

The invention relates to rotary electric switches and more particularly to the drum type, such, tor instance, as are used in controllers tor electric motor vehicles. It is the object olE the invention to obtain a construction which will give an exceedingly quick opening ot contacts and which is positive in its action and simple in its construction. To this end the invention consists in the con.- struction as hereinatter set forth.

In the drawings:

.Figure l is a plan view ot the switch; Figure 2 is a cross-section therethrough; and

VFigures 3 and fl are perspective views oi' the star wheels detached.

A is the drum or body of the rotary switch on which the contacts B are mounted to successively engage. the stationary brush contacts C. D and E are star wheels arranged in axial alignment with the drum, the 'former being txedly mounted to the end of the drum, and the latter having a limited independent rotation. These star wheels are adapted to cooperate with rollers F mounted upon levers or dogs Gr and Gr', which are under tension of springs H holding said rollers in engagement with the notches ot the respective star wheels. The star wheels l) and E are spaced trom each other and between the same is arranged a lug l projecting trom the one and a lug` J projecting from the other, said lugs being in radial alignment. K and K are springs, preferably leat springs, which are bolted or otherwise. secured to the lug l... as indicated at L, and which embrace the lug J. These springs extend beyond the axis of the drum and star wheels and the arrangement is such that when said star wheels are moved rota-- tively in relation to each other, one or the other ot' said springs will be flexed. This flexing will place a resilient torque upon the star wheel, which is not directly actuated, with the result that it will torce the roller F out ot engagement with the notch in the wheel and permit engagement in the succeed` ing notch.

It is desirable to make this action absolutely certain, giving' the drum an initial positivel start from rest, it necessary, after which the springs act instantaneously, and also to prevent too great a relative motion between the two star wheel-s. This is accomplished by a lost-motion coupling between the two star wheels, comprising a V-shaped lug M forming an extension from one star wheel, and' a V-shaped notch N of greater angle on the other star wheel in which the lug M engages. The clearance tor the lug M in the notch N is such as to allow the directly-actuated star wheel to move its roller F partly or completely out of engagement with its present notch before moving the other, thereby placing the springs under strain which imparts a snap-action to the drum, either when the spring strainalone becomes suiilcient to overcome the retaining action of the drum star wheel roller and contacts 'friction or when given an initial impulse by the lug M and notch N coming in contact. Further movement than d`esired is prevented by the retaining action ot the star-wheel rollers and the opposing action o'f the leaf springs. Also, when the cooperating star wheel is actuated, the firstmentioned star wheel will usually'complete its movement and will be re-engaged by the roller F before the second star wheel is fully disengaged `trom its roller F. Thus when the snap occurs, it will move the second star wheel to a position for engagement with the roller F and further movement will be prevented by the opposing spring. Therefore, while the movement which breaks electrical contact is very quick, this movement is arrested at an exactly predetermined point.

To hold the star wheels and drum in axial alignment and to provide means for actuating the star wheel E, these parts are mounted upon a shaft O, which is revoluble in bearings in the drum but is rotatively tilted to the y star wheel E. This shaft may be provided with any suitable actuating handle (not shown) by means of which it can be turned in either direction to cause the shifting of the switch trom one position to another.

That lf claim as my invention is:

l.. In an electric switch, the combination Awith a rotatable member having a plurality ot electrical contacts mounted thereon, ot a pair of star Wheels, one having a positive driving engagement with said membeil and the other having a limited relative movement thereto, yieldable dogs for engagement with the respective star wheels, a lost-motion positive drive connection from one star wheel to the other, permitting a movement olf the actuating member before positively comn'iunicating said movement to the actuated member, and a resilient torque connection between said star Wheels placed under tension by the initial movement of the actuating member.

2. In an electric switch, the combination with a rotatable member having a series oi contacts mounted thereon, oli a pair oi' star wheels, one being rotatiyely lixed thereto, resilient latch dogs for engaging said star wheels, a. lost-motion drive connection from one star wheel to the other, permitting o'" independent rotation through a predetermined angular distance, and a resilient torque connection between said star wheels placed under tension by the relative rotation thereof.

3. In an electric switch, the combination with a rotatable member and a series ol contacts mounted thereon, o'i' a pair oi star wheels, the one having a positive connection therewith, means Yfor rotatively actuating the other star Wheel, lugs projecting Arom said star wheels in radial. alignment, a spring secured to one oil said lugs and cngaging the other lug Yforyieldably holding the saine in radial alignment, a projection from one ol? said lugs engaging a recess in the other star Wheel forming a lost-motion driving connection between said star wheels, and resilient latch dogs for engaging said star wheels.

e. In an electric switch., the combination with a rotatable member having a series olf contacts mounted thereon, oil a pair ot star wheels, one being positively connected thereto, resilient latch dogs for engaging said star wheels, lugs proj ecting 'from said star wheels on opposite sides of the common axis thereof in radial alignment with each other7 springs secured to one of said lugs and embracing the opposite lug, and a projection Yfrom one of said lugs extending into a recess in the other star Wheel With clearance to torni a lost-motion driving connection.

5. In an electric switch, the combination with a rotatable member, of a series of electric contacts mounted thereon, a pair oi star wheels, one being positively connected thereto, resilient latch dogs tor engaging said star wheel, a lug on one of said star Wheels extending radially and crossing the axis thereo'li, a lug on the other star wheel extendingl in radial alignment with said Ifirst-nientioned lug on the opposite side of the axis, a pair o'lf leaf springs secured to the last-inentioned lug and embracing the first-inentioned lug, and a V-shaped lug projecting from one oic said lugs and engaging a V- shaped. aperture in the other star whe-eh the angle being such as to provide a lost-motion connection, for the purpose described.

ln testimony whereof a'llix my sigiiaturc.

ennfriss rIsMiTn. 

